In a statement, an ICO spokesperson said: “As with any new technology, we would expect Facebook to be upfront about how people’s personal information is being used.

“The privacy issues that this new software might raise are obvious and users should be given as much information as possible to give them the opportunity to make an informed choice about whether they wish to use it.

“We are speaking to Facebook about the privacy implications of this technology.”

‘Should have been more clear’

The company, led by founder Mark Zuckerberg, has admitted the roll-out process “should have been more clear”.

Facebook has agreed to provide European regulators with information about its use of the technology. But a spokeswoman for the world’s largest social network, which has more than 500 million active users, said there was no “formal investigation” under way.

It comes down to the question of should you be concerned about the potential for the authorities to be able to find you based on your looks. Zee M Kane, The Next Web

A spokesperson said: “We have noted the comments from some regulators about this product feature and we are providing them with additional information which we are confident will satisfy any concerns they will have.”

Zee M Kane, editor-in-chief of technology website The Next Web, told Channel 4 News: “The roll-out strategy was very poorly implemented and it’s not surprising there’s been uproar amongst users and the media.”

He added: “The technology isn’t currently able to search the entire site for a specific person’s face. That said, with the engineers at Facebook and the open source development of the technology, clearly the potential is there. As with many other privacy fears, it then comes down the question of should you be concerned about the potential for the authorities to be able to find you based on your looks.”

How does face recognition work?

Facebook’s new tool scans users’ newly uploaded photos, comparing the faces in the photos with previously labelled photos to see if it can match any of the people.

If a match is found, Facebook alerts the person uploading the photos and invites them to “tag”, or identify, the person in the photo.

Facebook said the product helps speed up the process of identifying people in photos, a popular practice among Facebook users that the company said currently happens more than 100 million times a day.

A spokesperson said: “Tag suggestions are only made to people when they add new photos to the site, and only friends are suggested. No action is taken on a person’s behalf, and all suggestions can be ignored.

“If for any reason someone doesn’t want their name to be suggested to their friends, they can disable the feature in their privacy settings.”

But the company concedes it is “not always going to be 100 per cent accurate” which could mean siblings and simliar faces are confused.

Zee M Kane told Channel 4 News it is not a huge departure from the current tagging process.

He said: “The only slight difference here is that it helps your friends spot you in photos when before they might have had difficulty doing so. The feature is an ‘auto-recommend’ feature rather than an ‘auto-tag’ feature.”

Mr Kane added that the technology itself is not new: “Facebook uses an open source project called OpenCV (Open Source Computer Vision Library), developed by Intel, that essentially lets anyone extract information from an image in real time to use for a particular purpose.

“In fact it’s been used on a number of sites – probably the most prominent being Google’s Picasa, which lets you organise your photos by the people in them.”

Would you be happy if Facebook used facial recognition on photos of you? Do you feel properly informed about changes to privacy settings?Innocent Mambo: No I wouldn't be pleased, and no I don't feel properly informed about the ever changing privacy settings either!Ali Howard: I'm going to tag them anyway myself so why not? Makes it easier for me.Mark Harris: I would have liked to have been notified of changes before they go live. Apparently I can control the information i 'share' this is frewuently a challenge without a crystal ball.Becky Rogers: No I wouldn't be happy. That should be up to us to tag our own photos.... and no we are not ever informed about setting changes... I know alot of people that shut there page down due to all this, and many more that are in the process... myself included.John Pearse: I found it quite creepy when it happened the other day. The first time I knew anything about it was when I uploaded some pics and a friend was automatically tagged before I'd done anything. But I was kind of relieved when it mistook me for someone else.Andrew Owgan: No, on both counts. The least Facebook could do is send a message to everyone telling us about the changes, how it works - and how to turn it off. Not too much to ask, I don't think.Karis Cooper: No, on both counts. Facebook is increasingly feeling less like a fun networking site, and more like a creepy surveillance tool.Add your voice now: Facebook.com/Channel4News or via Twitter @channel4news